Monday, 1 September 2008

Screw Top Pot

A day before going on holiday I decided I needed a container to store the lens adapter for my camera. The lenses have caps on each end, but they require and adaptor which is a bit delicate: - I knocked up an HDPE pot with a screw top lid that just the right size to hold it: - The outside diameter of the adapter is about 48.5mm so I made the pot I.D. 50mm to allow some clearance. It actually shrank to 48.5mm, so it is a snug fit. Lucky it didn't shrink any more! I made the thread using the helix tool in CoCreate. You draw a 2D profile and then use the helix tool to spin that round an axis, specifying the pitch. The dimensions were just a stab in the dark: I made the crest of the thread 0.8mm as that is two layers (Nyquist sampling theorem) and made the sides 1mm long 45° slopes, so that made the crest height 0.7mm. The minimum pitch with this profile would be about 3mm so I made it 3.5mm to give some clearance. I also made the the lid 1mm bigger radius so there is 0.3mm clearance from peak to corresponding valley. A couple of things I missed which would make it easier to engage: -
Despite this it works surprisingly well for a first attempt with an arbitrary profile and dimensions. I am slowly homing in on getting rafts peel-able for HDPE. I made this with the first layer outline hotter than its infill :-

HDPE.raft_temp = 215
HDPE.first_outline_temp = 230
HDPE.first_layer_temp = 205
HDPE.layer_temp = 240

Most of it peeled with a little encouragement from a chisel at one side.
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